Purpose: To explore the feasibility of a glaucoma stent with a titratable pressure-lowering effect.
Methods: This was an in vitro study. We created a resin stent with a micro-precision three-dimensional printer. It represented a cylinder with one primary and two secondary lumina. The inner opening of each secondary lumen was sealed with a membrane. We used a surgical eye model to simulate implantation of the stent and a laser procedure analogous to argon laser trabeculoplasty (ALT) to ablate each membrane. To study the fluid dynamics, we used a high-precision syringe pump and measured the steady-state pressure for one, two, and three lumina in parallel at flow rates of 2.5, 5.0, and 10.0 µL/min.
Results: The stent could be implanted into the eye model and visualized in the anterior chamber angle. Coloring the membrane facilitated laser membranotomy, and a 0.1-second laser pulse with 250-mW power was enough to ablate one membrane. The steady-state pressure for one lumen increased linearly with increasing flow rate, in accordance with the Hagen-Poiseuille equation. Two and three lumina in parallel decreased the pressure by factors of 2.1 and 3.2, respectively, in accordance with the electronic-hydraulic analogy and Ohm's law applied to parallel resistors.
Conclusions: The study presents proof of concept for a glaucoma stent with multiple lumina, which can be separately opened with an ALT-like procedure to induce a predictable, stepwise increase in pressure-lowering effect.
Translational relevance: The glaucoma stent in this experimental study can be reproduced in a biocompatible material and further studied in vivo.